Low-cost broadband circularly polarized probe-fed patch antenna for WLAN base station

Operation with CP (circular polarization) requires no strict orientation between the transmitter and the receiver for wireless communications, and is very suitable for applications in wireless local area network (WLAN) to overcome multipath fading problems and enhance system performance. However, for practical applications in the 2.4 GHz WLAN band (2400-2484 MHz), a wide CP bandwidth (larger than about 3.5%) is required. For this purpose, we demonstrate a novel and simple broadband circularly polarized patch antenna comprising a corner-truncated square patch, an L-shaped ground plane, and a single probe feed. The proposed antenna can be easily constructed at low cost, and have an impedance bandwidth (1:1.5 VSWR) of about 30%, a CP bandwidth (3 dB axial ratio) of about 10.4% and a gain level of 8.5 dBi or larger within the CP bandwidth. The obtained CP performance is among the best that have been reported for single-feed single-element patch antennas.